And then there is the eBay, unfortunately, which is pretty much the last of the resources on the Internet. I would suggest looking for filters here though.

The FE is one of the most popular Nikons but production has been stopped for many years now. That's why the parts for it are becoming scarcer every day. If there is a particular part you're after, the better option might be buying another used FE body and keeping the other one for spare parts.